Liquid pumps are used in many environments or applications. Such devices conventionally include a housing defining a pumping chamber or cavity within which an impeller assembly is rotated. The impeller assembly is mounted on shaft means rotatably journaled within the housing and including radially projecting impeller blades for drawing fluid into an inlet of the housing and out through an outlet. Bearings are provided about the impeller shaft often behind the impeller to journal the shaft within the housing. A pressure balance chamber normally is provided behind the impeller to reduce axial thrust loads thereby increasing the life, or reducing the size or quantity of the thrust bearings. The balance chamber is provided with communicating passageways to inlet or another low pressure reservoir In most instances these passageways are merely holes through the impeller shroud and situated between the inlet end of the impeller vanes where pressure is low. Leakage flow through the passageways reduces the pressure in the balance chamber and thereby reduces the axial thrust load that must be carried by the bearings.
In fuel boost pumps of the character described, it often is desirable to provide a liquid ring pump operatively associated with the main impeller pump for priming the pump system. In other words, where fuel is stored below the level of the impeller pump, the fuel must be lifted up the fuel line to the impeller pump, and the liquid ring pump performs this function.
This invention is directed to providing an impeller-type centrifugal pump system embodying both a pressure balance chamber and a liquid ring priming pump and communicating the chamber and the pump with the inlet side of the impeller means in a seriatum fashion through the balance chamber to the liquid ring pump.